Indexing device



Sept 15, 1953 Filed July 6. 1950 H. N. ROCKS INDEXING DEVICE 2 Sheets-Sheet l SePt- 15 1953 H. N. RocKs 2,651,895

INDEXING DEVICE Fued July e, 195o 2 sheets-sheet 2 Patented Sept. 15, 1953 UNITED STATES PATENT OFFICE INDEXING DEVICE Hugh N. Rocks, Waynesboro, Pa., assigner t'o Landis Tool Company, Waynesboro, Pa. Application July 46, 1950, `'Serial No. 172,257

(Cl. r51'-2-16) y13 claims. l

This invention relates to crank grinding inachinesy particularly to apparatus for indexing successive crankpins on a crankshaft to a position in which the entire crank will rotate about the axis of a given pin.

Present methods of vcrank grinding require that the rotation of the crank be stopped after the grinding of each pin so that the clamping fixture may be opened and the crank rotated relative thereto to bri-ng the next pin on center to be ground. By 'this method, a vconsidera-ble portion of the oorto-floor time for grinding crankshafts is taken up by this indexing voperation.

It is, therefore, an 'object of this invent-ion to provide means whereby the crank may be indexed angularly from one pin to another while the work is being traversed 'from one 'pin to another without stopping the rotation thereof.

A further object is to provide means whereby the crankshaft may be rotated independently of the clamping fixture and headstock spindle.

A further object is vto provide means for stop-- ping or retarding the rotation o the crankshaft while the rotation of the spindle and 'clam-ping xture continues.

A further object is to provide lan indexing apparatus and means for timing the 'operation thereof.

In the drawings,

Figure 1 is a fro-nt sectional elevation 'of va crank-driving headstock.

Figure 2 is a sectional View of a safety latch which permits a slight opening of the clamping xture for the purpose of indexing.

Figure 3 is a section along the line 3-3 of Figure l showing the apparatus for timing' the operation of the index mechanism.

Figure 4 is a combination hydraulic and electrical diagram showing the relation of this invention to the other parts of a crank grind-ing machine.

Numeral IU indicates the left-hand head of a crank grinding machine; H, a spindle rotatably mounted in bearings l2 and t3 sardi head. Said head is rotated by means of a 'motor (not shown) through a drive shaft i4, sprocket i5, chain belt I6, and 'sprocket I1 on the spindle II'I A clamping ii'xture 2id of this type is shown in Patent No. 1,816,750, granted July v28, 1593"1,

This parvticular clamping vfixture has one feature not dis closed in 'the above-mentioned patents. This Afeature consists of 'a latch member 25 resiliently urged by spring '2B into a recess 27 in clamping rar'rnil.

Latch -25 is an vextension of a piston 2Q, which may be actuated by fluid under pressure to withdraw latch '25 against the Aaction of spring' VLatch 425 serves to limit the movement ci clamping arm 28 so that lsaid clamp may release the crank suiicientiy to permit rotation thereof relative to the clamp, but not enough to permit the crank to be removed from the' holding iixtur'e. The -ainount which the crank may be opened is determined by 'the adjustment of screw.

The en'd oi' the crankshaft '2i has attached thereto an index plate 35 rotatably mounted on anti-friction bear-ings 3S in said clamping nxture 28. Said crank may be located relative to said index plate by means of a pin 252 mounted in iixe'd relation to plate 35 and adapted to enter a hole 2.3 in flange Y24 of crank` 2E. Said index plate has a number of equally spaced notches correspondingto the 'an u-Iar spacing or the pins 'on the crankshaft. this case, the shaft has hour pins spaced at ninety degrees. A plunger 3'1 is held against Said index plate b'y a Spring 3,8 and acts as a stop "to l'oc'f'ite said plate and the successive pins of said crankshaft in position 'to be' rotated' about their' own axes. Attached to said index platelis a-.sh'aft 46 having universal joints 4| and 42 at opposite ends thereof., joint M serving to lo'onlriecty 'said' shaft to said index plate. Joint 112 connectsshaft SEI with a shaft -502 4Said shaft 411 a connection with joint [a2 withl a resilient connection between said joint and said shaft vin. the' form' of. a spring 53.

Shaft serves as a means :for rotating several accessory devices such as the timing apparatus shown Figure 3, an. indexing switch 55, andan electrical brake rotor et.

Said timing apparatus consists of a housing if), through the 'center of which: passes a shalt 50. On' 'shaft 50'i'smounted a gear 'il in en gagement with a larger gear l2? on; a stubv shaft 13. Also mounted on said stu-b' shaft is an index plate 14 having unevenly spaced notches spaced according to the amount of angular index from one pin to another. vFor exaimile:4 The angular distance between adjacent pi-ns in the direction in which indexing takes place might be two or three times the angular distance betweensaid pins. In other' words, adjacent pins might be only 90 apart in one direction of rotation and might be 270 apart in the opposite direction. The connection between said timer index plate 14 and said stub shaft is spring loaded by springs 15. The speed ratio between gears 1| and 12 is 2:1 in this particular case, but it may be 3:1 or 4:1 as may be required for six cylinder or 8 cylinder in-line crankshafts. A plunger 16 forms the stem of a valve 11. Said plunger is held out of engagement with index plate 14 by means of a spring 18. Said plunger is urged into operative relation with said index plate 14 by fluid under pressure introduced at the end of the valve opposite said spring.

So long as said plunger is held away from index plate 14 by said spring 18, fluid under pressure is directed to hold plunger 31 out of engagement with index plate 35. The reason for the uneven spacing of the notches on index plate 14 is due to the fact that, while each of the four pins on the crankshaft has a different axis and the four axes are equally spaced, successive pins will not necessarily be ninety degrees apart. It is, therefore, necessary sometimes while indexing the shaft axially from one pin to the next, to index the shaft angularly through 180 or 270 degrees. In such cases, plunger 31 must skip one or two notches in index plate 35.

The means for effecting relative longitudinal movement between the work piece 2| and grinding wheel consists of a cylinder |40 in which is slidably mounted a piston |4|. Said piston may be connected through piston rod |42 to the work supporting carriage of a grinding machine (not shown). However, it is shown as connected to a spacing bar |43 which, in actual practice, is mounted on the carriage of the machine. Fluid under pressure for driving said piston |4| is supplied by pump 80 through line 8|, line 82 to reversing valve |50, through which it is directed alternately through line |5| to the head end 0f cylinder and through line |52 to the rod end of said cylinder. The means for stopping the longitudinal movement intermittently for grinding successive crankpins includes spaced notches |44 in spacing bar |43 corresponding to the spacing of the pins to be ground on the crankshaft.

Adjacent each of the end notches is a stop block |45 to prevent accidental movement of the carriage beyond the two end notches. In each of said notches is a vertical plunger |46, one end of which engages the actuating element of an electric switch.

A plunger |55 formed integrally with valve |56 is held in engagement with said spacing bar by spring |51. Said plunger may be withdrawn from said spacing bar by introducing fluid under pressure from line |60 into the upper end of said valve. Fluid under pressure for line |60 is supplied from a spacing valve |6| actuated in one direction by solenoid |62 and in the opposite direction by spring |63. Solenoid |62 may be energized by push button switch |64 to shift valve |6| to the left against spring |63. When so positioned, said valve directs fluid under pressure from line 84 through line |65 to said valve, which directs it through line |60 to `the upper end of plunger valve |56.

Operation With all parts in the position shown in Figure 4, clamping arms 28 are opened by pressing push button switch 90 to energize solenoid 9|, shifting latch valve 92 to the left against spring 93 and directing iuid lunder pressure from lines 84 and 94 through line 95 and lines 96 and 91 to shift latch pistons 29 against the action of springs 26 and thus withdraw latches 25 to permit opening of clamping arms 28.

A line 98 leads from line 91 to actuate valve |00, moving said valve to the left to block off pressure line |0| and connect line |62 with exhaust line |03. In the normal position of valve |00, fluid under pressure from line |0| passes through line |92, plunger valve |56, and lines |04 and |95 to clamping cylinders |20, actuating pistons |2| therein against the action of springs |22 to move clamping arms 28 into engagement with a work piece. With valve |00 under pressure from line 98 and line |02 connected to exhaust |03, the fluid for actuating the clamps is permitted to escape and the clamps are opened by springs |22.

An unground crank 2| is then placed in the clamps 28 and rotated until hole 23 in flange 24 is engaged by pin 22. The crank is then in position with No. 4 pin on center to be ground. Plush button switch is released, and fluid under pressure in line holding latches 25 in inoperative position and Valve |00 in the left-hand position is permitted to exhaust from valve 92 through exhaust lines ||5 and H6. Fluid under pressure from line |9| is then directed through valve |90 and line |02, plunger valve |53, and lines |04 and |95 to clamp cylinders |20 to move clamps 28 into contact with crank 2|. Releasing pressure in lines 96 and 91 permits springs 26 to move pistons 29 and latches 25 into the position shown in Figure 2. Reduction of pressure in clamp cylinders |20 will permit opening of said clamps, but only to an extent limited by latches 25. A slight adjustment of said opening may be effected by means of adjustable stops 30.

With the parts in the position shown, that is, plunger |55 in notch |44a and N0. 4 pin of crank 2| positioned to rotate about its own center, an electric circuit is closed by means of plunger |55, holding switch plunger |46 in position to close spacing bar switch 4. Rotary switch 55, which rotates with the crankshaft when it is being positioned angularly, is in position to close a `circuit to contact 4 thereon. Thus, the complete circuit is from LI through contact 4 of switch 55, line 4, spacing bar switch 4, and common line |10 to relay |1| of feed switch |12. Closing said switch energizes feed control solenoid |13.

When so energized, solenoid |13 shifts valve |14 to the left against spring |15, connecting pressure line 83 with line |16 to supply reversing valve |11. Said valve may be shifted manually by lever |18 to direct fluid under pressure alternately through lines |19 or |80 to the head end |8| or the rod end |82 of cylinder |83. Piston |84 in said cylinder is connected by means of piston rod |85 to a wheelbase (not shown) in which the grinding wheel |30 is mounted. Thus, unless the pin which has been placed on center corresponds to the notch in which the plunger is dropped, the circuit to relay coil |1| will not be completed; and switch |12 will remain open. Solenoid |13 will remain in the position shown, and valve |14 will be held by spring |15 in the position shown also to prevent a supply of fluid from reaching reversing valve |11. Under these conditions, therefore, the feed piston |84 is inoperative; and it is impossible to move grinding wheel |30 into grinding position with a pin which is not on center to be ground.

After pin No. 4 has been ground to size, the operator closes push button switch |64 to energize solenoid |82 and shift spacing valve |-6| to the left against spring |53. VIn this position, 'fluid under pressure from line 84 passes .through line |55 and is directed by valve |6| to line |60 leading to 4the upper end of plunger valve |56 and moving said valve downwardly against spring |51. When said plunger is withdrawn from notch |44a in spacing bar |43, fluid .under pres- Sure is directed through reversing valve |50 and line |52 to the left-hand end of cylinder |40 to shift spacing bar |43 and work piece 2| to the left.

In the withdrawn position, valve |53` connects lines |04 and |05, which supply .clamp cylinders |20, with exhaust passage 20.0. Lines `|04 rand `|05 thus permit the escape of fluid under pressure from clamping cylinders i3d, permitting clamp 28 to be opened by springs |22. The extent of this opening movement, however, is restricted by latches .25 so that the clamp 28 moves only enough to permit rotation of crank 2| therein.

Valve |56 also connects line |02 from valve |00 to direct fluid under pressure through line 205 :to timer valve 11. Fluid from line 205 passes through line 20B to the upper end of valve 11, urging it downwardly against spring 18. At the lower end of said valve is a plunger 16, which is 4held in engagement with timer index plate 14.

Line 205 also directs uid through valve 11 and line 20.1 to one end of cylinder 208 to shift piston 253 and plunger 31 downwardly against spring 33, withdrawing said plunger from engagement with index plate 35.

When plunger |55 is withdrawn from any of the notches in the spacing bar, a nnger 2 I5 thereon actuates switch 2|6 to energize magnetic brake 50. Plunger 31 and its associated actuating elements are mounted in clamping fixture 28. When said plunger is withdrawn from index plate 35 as described above, it continues to rotate at the same rate along with clamp 28. However, brake 60 on shaft 50 prevents continued rotation of said shaft and associated parts, as well as crank 2|, at the same rate as clamp 28. Thus, there is a relative rotating movement between plunger 31 and index plate 35, to which crank 2| is attached.

Said plunger 31 moves in a counterclockwise direction in Figure 4; and when moving in this direction, the angular spacing between pin No. 4 and pin No. 3 is 270 degrees` This means that plunger 31 must be held out of contact with index plate 35 until it has passed the notches corresponding to pins 1 and 2. This is accomplished by holding valve 11 in the position shown until plunger 31 has moved relative to index plate 35 between the notch corresponding to pin No. l and that corresponding to pin No. 3. Valve 11 is held in this position by timer index plate 14 which, as described previously, rotates at only half the speed of index plate 35.

VDuring a grinding operation, spindle shaft 50, timer housing 10, switch 55, and brake rotor 50 rotate as a unit. When said brake is energized, it retards the rotation of shaft 50; but the housing continues to rotate with spindle The extent of retardation of shaft 50 may be adjusted by adjusting the excitation of said brake. In actual practice, the shaft 50 is retarded but not stopped. However, for the purpose of simplifying the description, we will assume thatsaid shaft is stopped. Housing 10, including timer index plate 14, gear 12 attached thereto, and -valve '11., rotates in an orbital path about shaft 5|) and gear 1| thereon. The ratio between gear .1| and gear 12 is such that housing 10 must make two 6. complete revolutions while said gear 12 and plate 14 make one revolution. Therefore, while plate 14 rotates from notch 4 to notch 3 .an angular distance .of degrees, plunger 31 rotates in a counterclockwise direction from notch 4 of plate 35 past notches 2 and before reaching notch 3, which in this direction is spaced 27-0 degrees from 'notoh4.

When plunger 13 engages notch 3 on plate 14, it permits valve 11 to move to a position to connect line 201 from plunger cylinder 208 with exhaust line I5. Spring 38 then moves plunger 31 inwardly in time to engage notch 3 and stop the relative rotation between crank 2| and clamp 23. The angular position of rotating arm 55 of switch 55 has changed to close a circuit through contact 3. At `about the same time, plunger |55 drops into `notch |4419, stopping the longitudinal movement, traverse piston MI, spacing bar |43, and crank 2| with pin No. 3 in alignment with grinding wheel |35. -Plungcr |455, actuated by plunger |55, closes switch 3 which, along vwith contact 3 of switch 55, completes a circuit to energize feed relay |11.

Plunger valve |56 has returned to position to connect line t2 with lines |04 and 35 to close clamps 28. Since the shaft has been properly indexed, both longitudinally and angularly, and relay |1| energized to close switch |12, solenoid |13 shifts feed valve |14 to the left to make fiuid under pressure available for feeding grinding wheel |30 into position to grind pin No. 3.. The above-described cycle vis repeated until .all .the pins on the shaft have been ground.

After No. l pin has been ground, plunger l 55 is withdrawn from notch lflfld by closing push button switch |64 to energize solenoid |52 and shift valve |6| to the left, thus directing fluid under pressure from line 84 to line |55 to the top 4of plunger valve |55. Push button switch 22 is then closed to energize solenoid 22| and shift valve 222 to the left, directing fluid under pressur@ from line 84 through line 223 to the righthand vend of reversing valve |50. Said reversing valve is thus shifted 'to the left to -direct fluid under pressure from line 82 through line l5! to the left end of traverse cylinder |40. Piston |41, attached to the work carriage (not shown), and spacing bar |43 move lto the right along with work piece 2| to place said work 'piece in the position shown in Figure 4.

While plunger |55 has been withdrawn and valve |55 shifted to the lower position, iluid under pressure from line 205 is connected with line 205 to timing plunger valve 11 and plunger cylinder 208 to withdraw plunger 31 from notch on plate 35.

Withdrawal of plunger |55 is elTected through vnger 2|5, closing the circuit through switch 2|6 to energize magnetic brake 50. In the lower position of valve |56, lines |32 and |05 to clamping cylinders |20 are connected with an exhaust line, thus permitting opening of clamps 20 to the extent permitted by latches 25. Thus, when brake 60 is energized, the headstock spindle and clamping nxture continue to rotate at the same speed; but the speed of rotation of the crank is retarded so that the relative angular position of the crank and the clamping fixture is changed. In this case, plunger 31 is held out of engagement with index plate 35, while timer index plate 14 rotates through the distance from notch to notch 4, the equivalent of degrees of rotation of the index plate `35. Therefore, the crank 2| has been indexed angularly to the starting position with pin No. 4 on center.

Push button switch 90 is then closed to'energize solenoid 9i to shift valve 92 to the left and direct fluid under pressure from line 94 through lines S6 and 91 to Withdraw latches 25 to inoperative position against springs 2B. Clamps 28 may then be opened to full extent by springs |22 and the finished crank removed from the machine.

While the apparatus disclosed herein is for the purpose of stopping or retarding rotation of the crankshaft relative to the crank clamping fixture, the invention also contemplates apparatus for driving the crankshaft temporarily at a speed greater than the clamping fixture.

I claim:

1. In a machine for grinding crankshafts, a pair of headstocks, each having a spindle, a clamping fixture rotatably mounted thereon for holding a crankshaft eccentrically whereby to rotate the shaft about the axis of one of said pins, means for rotating said splindle and fixture, means for indexing said shaft angularly in said fixture, including an index plate eccentrically mounted relative to said spindle axis and having connection between said index plate and said crank shaft, a shaft rotatably mounted in the outer end of said spindle and having a braking mechanism thereon, said second shaft connecting said index plate and said first mentioned shaft.

2. In a machine for grinding crank shafts having a plurality of axially and angularly spaced crank pins thereon, a work support, a pair of axially spaced work heads thereon, each having a spindle rotatably mounted therein, a clamping xture rotatably mounted on said spindle for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, an index plate rotatably mounted in said fixture and having notches corresponding to the angular spacing of said crank pins, a plunger on said fixture for locking said index plate against rotation relative to said clamping fixture, an index shaft one end of which is attached to said index plate and therefor eccentric with respect to said spindle, the other end being concentric with said spindle, said shaft being normally rotatable in fixed relation with said spindle and braking means attached to the concentric end of said shaft for retarding or stopping rotation thereof with said spindle.

3. In a machine for grinding crank shafts, having a plurality of axially and angularly spaced crank pins thereon, a pair of headstocks each having a clamping fixture rotatably mounted therein for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, means for indexing said shaft angularly in said clamping fixtures comprising an index plate having notches corresponding to the angular spacing of said crank pins, a plunger on said clamping fixture for locking said index plate against rotation relative to said clamping fixture, a piston on said plunger, means for causing said index plate to rotate temporarily at a rate different from the rate of rotation of said clamping fixtures, said means being effective also to direct fluid under pressure to withdraw said plunger from said index plate.

4. In a machine for grinding crank shafts, having a plurality of axially and angularly spaced crank pins thereon, a pair of headstocks each having a clamping fixture rotatably mounted therein for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, means for indexing said shaft angularly in said clamping fixtures comprising an index plate 'having notches corresponding to the angular spacing of said crank pins, a plunger on said clamping fixtures for locking said index plate against rotation relative to said clamping fixtures, a piston on said plunger, means for causing said index plate to rotate temporarily at a rate different from the rate of rotation of said clamping fixtures, said means being effective also to direct fluid under pressure to withdraw said plunger from said index plate, and means for effecting said index movement through an angle greater than the angle between adjacent crank pins comprising a secondary index plate having unequally spaced notches therein and geared to said rst index plate to rotate at a fraction of the speed of said index plate and a valve actuated in conjunction with said secondary index plate for directing fluid to withdraw said firstmentioned plunger and to prevent said plunger from entering one or more notches on said first index plate.

5. In a machine for grinding crank pins, a work support, a pair of headstocks rotatably mounted thereon, a grinding wheel support, a grinding wheel rotatably mounted thereon, means for effecting intermittent relative longitudinal movement between said supports comprising a motor attached to said work support, a spacing bar having notches spaced according to the pins on the crank shaft, a plunger for engaging said notches, clamping fixtures rotatably mounted in each of said headstocks for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of the pins, means for indexing said shaft angularly comprising means for retarding rotation of said shaft while said clamping fixtures rotate through an angle equal to the angle between adjacent crank pins, control means for initiating said longitudinal movement of said carriage, said control means and said retarding means being actuated by said plunger upon withdrawal thereof from said spacing bar.

6. In a machine for grinding crank pins, a work support, a pair of headstocks mounted thereon, each having a clamping fixture rotatably mounted thereon for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, means for indexing said shaft angularly comprising means for retarding rotation thereof while said clamping fixtures rotate through an angle equal to the angle between adjacent crank pins, a grinding Wheel support, a grinding wheel rotatably mounted thereon, means for effecting intermittent relative longitudinal movement between said work supports and said grinding wheel support comprising a motor for moving said work support, a spacing bar having notches spaced according to the spacing of the pins of the crank shaft, a plunger for engaging said notches, control means vactuated by said plunger upon withdrawal from vsaid spacing bar for initiating said longitudinal movement of said carriage and additional control means operable by said plunger for actuating said retarding means.

7. Apparatus for grinding crank shafts having la plurality of axially and angularly spaced crank vspacing of the pins on said crank shaft and a plunger for engaging said notches, a clamping xture rotatably mounted in each of said headstocks for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, means for indexing said shaft angularly relative to said headstock, a multi-pole switch having an element rotatable with said shaft during said angular index thereof, a switch in each of the notches of said spacing bar, each of said switches in said spacing bar being connected in series with one of the poles in said multi-pole switch and with said transverse moving means, said spacing bar switches being actuated by said plunger when it enters each notch.

8'. In a machine for grinding crank shafts having a plurality of axially and angularly spaced crank pins thereon, a work support, a pair of axially spaced work heads thereon, each having a spindle rotatably mounted therein, a clamping xture on said spindle for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, an index plate eccentrically and rotatably mounted in said xture coaxially with said crank shaft and having peripherally spaced notches corresponding to the angular spacing of said crank pins, a plunger on said fixture for engaging said notches for locking said index plate against rotation relative to said clamping xture, braking means for retarding or stopping rotation of said index plate and crank shaft about their common axis.

9. In a machine for grinding crank shafts having a plurality of axially and angularly spaced crank pins thereon, a Work support, a pair of axially spaced work heads thereon, each having a spindle rotatably mounted therein, a clamping iixture on said spindle for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, an index plate eccentrically and rotatably mounted in said fixture coaxially with said crank shaft and having peripherally spaced notches corresponding to the angular spacing of said crank pins, a plunger on said fixture for engaging said notches for locking said index plate against rotation relative to said clamping fixture, braking means for retarding or stopping rotation of said index plate and crank shaft about their common axis, means operated in timed relation with said braking means for withdrawing said plunger from said index plate whereupon said spindle rotates relative to said plate until said plunger drops into another notch and thereby locates another crank pin on center to be ground.

10. In a machine for grinding crank shafts a pair of headstocks each having a clamping xture rotatably mounted therein for holding the crank shaft eccentrically whereby to rotate the shaft about the axis of one of the pins, means for closing said clamping fixture to hold a crank shaft rigidly for a grinding operation, and for opening said clamping xture to place a crank therein or to remove a crank therefrom, means for indexing a shaft angularly comprising means for retarding rotation of said shaft while said clamping fixtures continue to rotate through an angle equal to the angle between adjacent crank pins and means for restricting the opening of said clamping fixture to an extent suificient only to permit such relative rotation between said crank shaft and said clamping fixture.

11. In a machine for grinding crank shafts having a plurality of axially and angularly spaced crank pins, a Work support, a pair of headstocks rotatably mounted thereon, a grinding wheel support, a grinding wheel rotatably mounted thereon, means for effecting intermittent relative longitudinal movement between said supports to successively position said spaced crank pins in operative relation with said grinding wheel, a clamping fixture rotatably mounted in each of said headstocks for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, means for indexing said shaft angularly in said iixtures, means for opening said clamping xtures to permit said angular indexing, and means for limiting the extent of opening said clamping fixtures for indexing.

12. In a machine for grinding crank shafts having a plurality of axially and angularly spaced crank pins, a work support, a pair of headstocks rotatably mounted thereon, a grinding wheel support, a grinding wheel rotatably mounted thereon, means for effecting intermittent relative longitudinal movement between said supports to successively position said spaced crank pins in operative relation with said grinding wheel, a clamping fixture rotatably mounted in each of said headstocks for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, means for indexing said shaft angularly in said fixtures, means for opening said clamping xtures to permit said angular indexing and means for limiting the extent of opening of said clamping fixtures for indexing, comprising an adjustable stop on said xture and a latch movable into and out of the path of said stop.

13. In a machine for grinding crank shafts, having a plurality of axially and angularly spaced crank pins, a work support, a pair of headstocks rotatably mounted thereon, a grinding wheel support, a grinding wheel rotatably mounted thereon, means for effecting intermittent relative longitudinal movement between said supports to successively position said spaced crank pins in operative relation with said grinding Wheel, a clamping fixture rotatably mounted in each of said headstocks for holding a crank shaft eccentrically whereby to rotate the shaft about the axis of one of said pins, means for opening said clamping xtures to permit said angular indexing and means for limiting the extent of opening of said clamping fixtures for indexing, comprising an adjustable stop on said fixture, a latch movable into and out of the path of said stop, and means for moving said latch from the path of said stop after all the pins on a crank shaft have been ground.

HUGH N. ROCKS.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date Re.21,582 Klingele Sept. 24, 1940 2,131,233 Ott et al Sept. 27, 1938 2,506,495 Flanders et al. May 2, 1950 FOREIGN PATENTS Number Country Date 570,001 Germany Jan. 19, 1933 

